A quick-thinking taxi driver is South Korea's latest hero. He alerted authorities after noticing suspicious-looking men, which led to the exposure of one of the biggest infiltrations of North Koreans to the South in years. Driver Lee Jin-kyu's reward could reach US$200,000 (HK$1.54 million), the most a citizen can receive for reporting and helping in the seizure of a North Korean vessel. Mr Lee said he saw the men in orange life jackets crouching by the side of the road and was 'suspicious they could be spies'. 'I drove back slowly to check out the site and found a black object making a strange noise and sparks.' Rewards are generous to civilians who help to track down spies - US$130,000 for information leading to the arrest of a spy, and US$40,000 for a leftist activist. Rewards have tripled recently with 'spies wanted' posters up countrywide. 'About 60 to 70 per cent of all spies caught are caught thanks to civilian reports,' said Yoo Dong-ryul, senior researcher at the Strategy Institute to Counter North Korea.